I have installed GTranslate Pro and when I trying to translate some page of my site it shows me partially translated page. In debug.txt is 414 error request: http://summer-in.com/toolarge.html. Pages with little content translates fully. How can I translate all my pages with Gtranslate Pro?

You should find the long test it tries to send to google for translation. Try to wrap some parts of the text with <span></span> tag, so it will be send part-by-part. Ex. Long - long - long text should become to <span>Long</span> - <span>long</span> - <span>long</span> text.